Using AC unit run-off water with low pH and TDS

[Zoren]

Good afternoon members. As I have posted, I bought a portable A/C for my orchids (I keep them in a closed in Florida room), because it gets to hot in the room (as high as 110 F in the summer) and the temperature doesn't go down very much at night. Even in the winter the room temperature has never gone down lower than maybe 70 F. It seems to me my plants seem happier now. I have gained another positive benefit from the A/C 'run off water'. When I run it, I get any where from 1.5 to 3 gallons of water. The PH and TDS readings seem to be as low as 'distilled water'. I've started using the water for my plants (I grow S/H now). My questions are: 1)Is anyone else using A/C water and is it working for you? 2)If the PH is low should I increase it? If yes, what should I use to increase the PH (right now the PH is at about 3.5 after I added 1/4 tsp. of MSU fertilizer to a gallon of the water). The PH is around 3.3 to 3.5 before adding fertilizer. I would appreciate any opinions and suggestions from members. Thank you all in advance..Zoren...

[rbarata]

I think you're making some confusion...PH as low as 2 to 3,5 is what you find in strong acids (a concentrated solution of Sulfuric Acid - H2SO4 has a PH of 1,5).

Now, regarding the A/C...are you sure it's not a dehumidifier? I think it's strange an A/C to produce so much water.

[Zoren]

rbarata, thank you for giving your thoughts on the subject of "my Portable A/C run off or captured water". This PH and orchid plants is new to me (meaning I never paid attention to PH before). So I checked the water I captured from the A/C again, with out doing anything to the water the PH is 3.3-3.5 (not much different from after adding MSU) and the TDS reading is 5 ppm. As for the A/C water captured, my A/C has 3 different positions Fan only, Dehumidify only and A/C only. I run it at A/C only and I capture 1.5 to 3 gallons when I run it for 8 hrs. at night. I am going to edit my 'thread' as to to PH I quoted before (sorry for the mistake). So, I'd still like some more feed back as to my using 'captured' A/C water. As to how to increase the PH I found out that using 'baking soda' should do the trick. What should be the optimum PH for growing orchids.....Zoren...P.S. My Portable A/C is a Wynter 13,000 BTU A/C, which is highly recommended for Growing Orcdis or other plants, fruits and vegetables...Zoren...

[Roberta]

OOOOHHH... Don't use baking soda! It contains sodium (as sodium bicarbonate) which is really bad for orchids. You may not see the effect right away, but it's definitely not good. I suggest simply mixing that ultra-pure water with some tap water. Most orchids, even the most sensitive, will be fine at a TDS of 30 ppm or so, that's still pretty pure. And it only takes a little tap water (if there is any hardness at all) to get the pH into a better place (5.5-6 would be great) without affecting the TDS much.

[Zoren]

Roberta, thank you for your input. Now as always in the orchid world, there are apposing opinions and for me this is a prime example of 'different' resolutions for a similar problem. Roberta, you say 'No to Baking Soda' because of the 'sodium' yet in my research others have said that 'baking soda..is the most stable of PH raising and stable way of increasing PH'. The biggest problem to 'me' (one of maybe millions of people) what is the correct way of 'Keeping, Raising, Understanding, Growing and understanding the chemical (having to do with PH & TDS of Water) in Orchid growing. The research I did came from a reputable Orchid grower who said ...'backing soda is the best way of raising PH with stable results' ..So, what is the real answer to the problem...Zoren...

[Roberta]

Baking soda would do the job with the pH, but of course that's not the only factor. If it were necessary to use a chemical method to control pH, I would think that calcium carbonate would be better. (Same carbonate ion doing the buffering (stabilizing pH) , but calcium is far more benign for plants (not just orchids). Dissolve in water and use a VERY small amount. In looking at orchid growing advice in general, back off and evaluate based on the questions "What does it do, why and how?" and "What am I trying to accomplish? Are there side effects?" There is usually more than one "right" answer, to get to the solution you seek. Here, you're looking at a bit of fundamental chemistry. Pure water tends to be acidic since it picks up carbon dioxide from the air. It has no buffering capacity (ability to resist changes in pH). What you want to do is add "something" that will resist pH changes - make the water a little less "pure" but stabilize the pH. Whether tap water works depends on the minerals (or lack of them) that it already contains. If it is "hard" - lots of carbonate, usually calcium bicarbonate, there's your calcium source. It only takes a little. If it is high in sodium, or is acidic or otherwise undesirable, not so much. Take a look at the water quality report from your water supplier (probably available on line) Knowledge is power...

[camille1585]

I'm moving your thread to a more appropriate forum, as this isn't really an introduction thread. And if you don't mind, I'm also changing the title of this thread make it more informative. Please let me know if you want a different title from what I proposed.

Given the hassle of adjusting the pH, would it not be easier to either not use that water at all or mix it with tap water? I really wonder what the AC unit is doing to the water. Water with such a low TDS (essentially pure water) usually has a pH of 6-7 or so. Rain water is around 5.5 due to the dissolved gases picked up by the rain drops.

[Subrosa]

Water produced by an a.c. or dehumidifier is essentially distilled water. It's produced by condensation of water vapor from warm humid air on the cold side coil. The process is the same with either or of unit.

[rbarata]

As Camille said, maybe there's water contamination.
Such a low ph should not happen as a byproduct of an air cooling process.

[camille1585]

Another question: what are you using to measure the pH (and TDS)? Cheap meters are generally not very accurate, and even expensive pH meters do need to be calibrated on a regular basis. pH strips or test paper (as used by aquarium hobbyists or for pool water) are low tech, but generally rather accurate for our uses.